Fending Off Infection in the Urinary Tract

Research UpdateJan. 9, 2013

Recent study has shown that ribonuclease 7 (RNase 7) contributes to defense of the human urinary tract against bacterial infection. The urinary tract is the body’s drainage system for removing wastes and extra water. The system includes two kidneys, two ureters, a bladder, and a urethra. Despite its proximity to the anus, the urinary tract is usually sterile—but how it maintains its sterility is not well understood.

Building on previous research that demonstrated that RNase 7 is produced in human tissues (free of microscopic signs of disease or inflammation) of the bladder, ureters, and a specific part of the kidney called the collecting tubule, and is present in uninfected urine in sufficient quantity to kill bacteria, the same group of investigators has now reported the initial characterization of the antimicrobial features of RNase 7 in the human urinary tract during infection. Significantly more RNase 7 was detected in acutely inflamed kidney tissue compared to either non-inflamed or chronically inflamed kidney tissue. Consistent with findings included in the scientists’ earlier study, non-inflamed collecting tubule produced RNase 7, as did acutely inflamed and chronically inflamed collecting tubule. However, in contrast to the non-inflamed condition, the kidney’s proximal tubules produced RNase 7 in the setting of acute and chronic inflammation. The urine from children with bacterial infections contained significantly more RNase 7 compared to urine from uninfected children. RNase 7 was shown to be a potent, broad-spectrum antimicrobial agent against different types of bacteria (scientifically categorized as Gram-positive and Gram-negative), which are commonly found to cause urinary tract infections. RNase 7 exerts its antimicrobial activity by disrupting the bacterial cell membrane—making perforations such that the bacterium is no longer self-contained.

This study adds considerable knowledge to understanding how the urinary tract maintains sterility. Future studies that reveal the regulatory machinery involved in RNase 7 production or detail how this protein exerts its antimicrobial activity at the molecular level may help develop new therapeutic approaches to maintaining the sterility of the human urinary tract.